Utilization and Yield of Nerve Conduction Studies and Electromyography in Older Adults

S Mello, O O’Toole, B Mcnamara

Cork University Hospital, Wilton, Cork

Abstract

Older adults are at increased risk of both central and peripheral neurological disorders. Impaired nerve and muscle deficits contribute to morbidity and reduced quality of life. Our aim was to define the utilization and yield of nerve conduction studies (NCS) and electromyography (EMG) in older adults. We reviewed NCS and EMG records for all patients older than age 65 in the year 2012. Of 1,530 NCS and EMGs performed, 352 (23%) were in patients older than 65 (mean age 73.7, 52% male). Two hundred and eighty-eight (83.7%) of NCS were abnormal as were 102 (71.8%) of EMGs. The likelihood of having an abnormal test result increased with increasing age. The most common diagnosis was peripheral neuropathy 231 (65.4%). The incidence of peripheral neuropathy is particularly high in this age group, and detection is vital to prevent morbidity and improve quality of life.

Introduction

The incidence of pathological processes resulting in changes in the latency, velocity or amplitude of nerve conduction peaks in persons over the age of 65. This can be attributed to conditions that are more common in the older population such as nutritional deficiencies, diabetes mellitus, malignancy and osteoarthritis, to name a few. Even in the healthy older patient, some decline in the neurological function of the peripheral nervous system is inevitable with the aging process. Impaired nerve function contributes to morbidity and a poor quality of life, leaving older persons susceptible to ulcers, falls and reduced mobility. The aim of this study is to define the utilization and yield of nerve conduction studies (NCS) and electromyography (EMG) in a homogenous population of older adults in the Southern region of Ireland.

Methods

NCS and EMG records for all patients older than age 65 in the year 2012 were reviewed. Normative values for NCS were taken from historical, published controls1,2. Three hundred and fifty-two records were identified during this period. Patient demographics were described. Diagnoses were recorded as neuropathy, myopathy, radiculopathy, plexopathy, anterior horn cell syndrome, unclear and multiple diagnoses. These categories were further stratified to detail the type and number of nerves involved. We also examined the referral forms and recorded data including the source and reason for referral, whether a provisional diagnosis was included in the referral and if so, if this was congruous with the post-test diagnosis.

 

Results

In 2012, a total of 1,530 NCS and EMGs were performed in the Munster region. Of these, 352 (23%) were in patients aged 65 and above. The average age was 73.7 (65-90), with 66 (18.8%) over age 80. Males comprised 52%. The majority of patients 330 (94%) were referred for testing to establish a diagnosis while 22(6%) were referred for disease prognosis. Most patients were referred by a medical consultant 167 (47.4%), followed by surgeons 76 (21.6%), neurologists 70(19.9%) and general practitioners 39 (11.1%). 294 (70.7%) of referral forms included a clinical question with potential diagnosis. Of these, 111 (37.8%) differed from the actual diagnosis as established by NCS or EMG. Of all NCS performed, 288 (83.7%) were abnormal as were 102 (71.8%) of EMGs. The likelihood of having a normal test result decreased with increasing age. Only 7% of patients over 80 had a completely normal result, as compared to 12% in those under 80 years of age. By far the most common diagnosis was neuropathy 227 (64.6%) followed by a normal study 39 (11.1%), multiple diagnoses 23 (6.5%), radiculopathy 16 (4.5%), anterior horn cell syndrome 12(3.4%), plexopathy 10(2.8%), unclear diagnosis 10 (2.8%) and myopathy 8 (2.3%). The most common type of neuropathy was a mixed polyneuropathy 215 (61.2%).

Discussion

While only 11% of the Irish population is above the age of 65, a disproportionately large (23%) of NCS and EMG were performed in this age group. The yield was high in this population and the likelihood of having an abnormal test result increased with age. It has been previously estimated that neuropathy is present in over 50% of diabetic patients over the age of 604, and in greater than 50% of all persons aged older than 803. Clinicians should bear this in mind when assessing older adults with functional decline or pain syndromes. Furthermore, the post-test diagnosis differed from the original clinical suspicion in almost 40% of cases, indicating usefulness of NCS and EMG in determining patients’ health outcome and treatment. This study had some limitations. Due to the retrospective nature of this study, limited patient data was available to us, thus we did not record patient comorbidities, clinical findings or treatments. Furthermore, we recognize that there is a need for up to date normal controls for NCS, especially in unwell older patients. This can perhaps be done by extrapolated norms in future studies5. In summary, NCS and EMG are useful tests for evaluation of a wide variety of peripheral nervous system abnormalities that commonly affect older individuals. The incidence of neuropathies is high in this age group, and as such, detection is vital in order to prevent morbidity.

Correspondence: S Mello

Cork University Hospital, Wilton, Cork

Email: smello7@hotmail.com

References

  1. Falco FJ,Hennessey WJ, Goldberg G, Braddom RL. Standardized nerve conduction studies in the lower limb of the healthy elderly. Am J Phys Med Rehabil.1994 Jun;73:168-74
  2. Falco FJ,Hennessey WJ, Goldberg G, Braddom RL. Standardized nerve conduction studies in the upper limb of the healthy elderly. Am J Phys Med Rehabil. 1992 Oct;71:263-71
  3. Mold JW, Vesely SK, Keyl BA, Shenk JB, Roberts, M. The prevalence, predcitors and consequences of peripheral sensory neuropathy in older patients. J Am Board Fam Pract. 2004 Sept-Oct;17:309-18
  4. Young M, Boulton AJM, Macleod AF, Williams DR, Sonsken PH. A multicentre study of the prevalence of diabetic peripheral neuropathy in the United Kingdom hospital clinic population. Diabetologia. 1993 Feb;36:150-54
  5. Jabre JF, Pitt MC, Deeb J, Chui KH. E-Norms: a method to extrapolate reference values from a research population. J Clin Neuropsychol 2015 Jun;:265-70

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